In the design of thin film magnetic recording media devices, it is important to provide a protective coating on the uppermost surface of the device to assure durability and reliability. Hydrogenated diamond-like carbon (DLC) is a hard, wear-resistant material that has a relatively low friction coefficient. It has been used as a protective coating in magnetic recording media devices such as thin film magnetic disks and magnetic recording heads.
For instance, U.S. Pat. No. 4,647,494 and U.S. Pat. No. 5,159,508 disclose the coating of a thin layer of hydrogenated carbon film onto a magnetic recording disk and a magnetic head slider, respectively. However, the method disclosed by both patents requires the application of an additional adhesion promoter layer onto the substrate before the final coating of the hydrogenated carbon can be applied. The patents therefore describe a two-stage deposition process. The tribological performance of these devices must be improved through the use of liquid lubricants on the surface of the protective DLC coating. In a modem recording device with reduced head-to-disk distance for increased recording densities, elimination of the extra lubricant layer is desirable. The removal of the liquid lubricant is also desirable for the elimination of capillary forces and meniscus formation which can cause increased stiction. The application of liquid lubricants to magnetic disk surfaces requires several processing steps, the elimination therefore reduces the manufacturing costs of such disks.
One method to eliminate the need of liquid lubricant is to further reduce the friction coefficient of the DLC coating. Such a method is disclosed by Miyake et al., in J. Tribol. Trans. ASME 113 (1991) 384. Approximately one micron thick of silicon-containing carbon films are first deposited by electron cyclotron resonance deposition and then the specimen surface is fluorinated by exposure to a CF.sub.4 plasma. It was shown that surface fluorination of DLC can reduce the friction and microwear of DLC films. Since the fluorination process is performed subsequent to the deposition of the DLC film, the fluorination is limited to the uppermost layer of the coating. As the wear of the coating removes the fluorinated layer, its lubricating advantage is lost after a relatively short wear time. The advantage of fluorination could be extended if it occurs throughout the entire thickness of the protective layer to maintain wear resistance.
Fluorinated DLC films have been previously prepared by others. For instance, Seth et al., reported in Thin Solid Films, 230 (1993) 90 that high fluorine content of films leads to a large drop in density which indicates a comparatively open structure of the films. The films were found to be extremely soft and had no wear-resistance.
It is therefore an object of the present invention to provide a fluorinated DLC protective coating for magnetic recording media devices that does not have the shortcomings of other conventional protective coatings.
It is another object of the present invention to provide a fluorinated DLC protective coating for magnetic recording media devices that does not require the use of additional liquid lubricants on its surface in order to provide adequate wear-resistance.
It is a further object of the present invention to provide a fluorinated DLC protective coating for magnetic recording media devices that has superior wear-resistance throughout its entire coating thickness such that its wear-resistance property does not deteriorate with the wear of the uppermost layer.
It is another further object of the present invention to provide a fluorinated DLC protective coating for magnetic recording media devices that can be applied directly to the uppermost surface of the devices without an intermediate adhesion promoter layer.
It is yet another object of the present invention to provide a fluorinated DLC protective coating for magnetic recording media devices that has superior wear-resistance and reduced stiction properties.
It is yet another further object of the present invention to provide a fluorinated DLC protective coating for magnetic recording media devices that can be deposited in a plasma enhanced chemical vapor deposition chamber at temperatures below 250.degree. C.